This invention concerns forming lines of weakness in portions of automotive trim pieces overlying airbag safety devices, in order to allow one or more airbag deployment doors to be created when an airbag is inflated.
Airbag safety systems are widely used in automotive vehicles and generally comprise an inflatable cushion, referred to as an xe2x80x9cairbagxe2x80x9d, stored folded in a receptacle and then rapidly inflated when a collision of the vehicle is detected by sensors.
The folded airbag is typically mounted behind an automotive interior trim piece such as an instrument panel or a steering wheel cover. One or more airbag deployment doors are forced open when the airbag is inflated to allow deployment of the airbag through the opening created by the deployment door movement.
During the last few years, airbag deployment doors that are integrated into the trim piece overlying the airbag receptacle have gained wide acceptance. As described in U.S. Pat. Nos. 5,082,310 and 5,744,776, these integrated doors employ a seamless or invisible construction whereby the deployment door or doors, although part of the trim piece, are not separately delineated and/or visible from the passenger side of the trim piece.
For such integrated deployment doors to open during airbag deployment necessitates weakening portions of the trim piece in order to allow trim piece sections to break free and hinge open. Weakening of the trim piece is carried out by creative lines of weakness comprised of scored lines formed by removing material from the trim piece from the back surface along a predetermined deployment door pattern. A critical component of this process is the amount of the trim piece material removed and/or remaining after cutting the score line. Accurate control of this process is critical to reliably producing proper airbag deployments.
A widely used method for determining the extent of material removal during scoring involves the use of triangulation type sensors as described in U.S. Pat. No. 5,883,356. These sensors, however, due to their triangulation operating principle, are limited in their ability to reach the bottom of the scoring produced by the cutting device. This is particularly so for narrow, deep penetrations which may be imparted by cutting devices such as lasers and cutting knives. Furthermore, due to their offset mounting, these sensors are not well suited to measure the varying penetration depth that occurs during scoring at a specific location. This is especially true if the scoring penetration is in the form of partial perforations or slots. As such, the process does not lend itself to scoring the trim piece in an adaptive control mode, where both depth sensing and scoring are in registry with each other to impinge the same point on the trim piece, during the progression of scoring of the trim piece.
Accordingly it is an object of this invention to provide a process and apparatus for scoring trim components overlying airbag installations in a manner that provides accurate adaptive process control, single-pass processing, improved airbag door deployment, and lower manufacturing costs.
According to the invention, the scoring of the trim piece is accomplished by the use of a controllable cutting means, such as a laser beam, which, based on feedback from two sensors, is controlled in intensity together with controlled relative movement between the laser and the trim piece, producing a precise, predetermined penetration into the trim piece along a predetermined pattern.
In this process, the laser cutting beam and sensing beam emitted from a first sensor are both directed at a surface on one side of the trim piece. A second sensor may also be positioned on the opposite side of the trim piece in opposition to the cutting laser beam. A beam combining device combines the laser cutting and sensing beams together so as to have collinear segments directed at exactly the same point on the trim piece. The scoring of the trim piece is carried out by the laser beam while the trim piece is moved in a predetermined pattern relative to the laser to form one or more deployment doors defined by the sections of the trim piece within the pattern. The depth of scoring of the trim piece by the laser beam is controlled by real time feedback signals corresponding to the depth of the cut provided by the first sensor. To determine material thickness remaining during scoring of each point along the predetermined pattern, real time feedback from the second sensor can be provided combined with the feedback signals from the first sensor. The sensor feedback can also be utilized to control the movement of the trim piece relative to the laser beam to enhance the weakening process control.
This process, due to the collinear arrangement of the impinging segments of the sensor and cutting beams, affords several advantages, including single-pass adaptive processing, scoring precision and superior part to part repeatability. The process is also independent of cutting depth, angle of cutting, scoring patterns, material inconsistency, material color, and surface grain variations.
Relative motion between the trim piece and the cutting beam to score the trim piece in a predetermined pattern can be provided by different means, including robots and X-Y tables.
The trim piece can have a monolayer, multilayer, or composite construction and could be scored on either side. The scoring can be continuous, intermittent or be a combination of both, and extend completely through one or more layers of the trim piece. The trim piece can be a finished part or a component which is subsequently integrated into a finished part.